Sieges of Mantua, (1796-1797)

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The sieges of Mantua played a key role during the third stage of Bonaparte’s campaign in northern Italy in 1796-1797, influencing for eight months (June 1796- February 1797) the development of all military operations. Four times the Austrians failed to relieve Mantua despite a huge expenditure of manpower and equipment that strained their military resources. On the other hand, the constant need to keep a strong blockading force around Mantua prevented Bonaparte from maintaining a sure grasp on northern Italy and prosecuting the war to the Austrian borders. The fall of Mantua on 2 February 1797 eventually allowed the Armée d’Italie to march to Frioul and sped up the course of events leading to the end of Bonaparte’s first Italian campaign and the conclusion of the Treaty of Campo Formio.

Mantua was the southwestern endpoint of a fortress system known as the Quadrilateral that stood between Lake Garda (to the north), and the rivers Po (to the south), Mincio (to the west), and Adige (to the east). A Renaissance city, Mantua lies on the right bank of the Mincio, where the river widens, forming an oblong lake. In 1796 the lake and swampy ground covered the northern, northeastern, and western accesses to the city. To the south and southeast lay another swampy area and a canal. More than anything else, it was this natural protection that made Mantua a formidable stronghold and caused enormous problems to any besieging force, not least the spreading of malarial fevers (the latter, admittedly, plaguing also the besieged).

The city was surrounded by an impressive extension of stone walls, bastions, outworks, and entrenchments, with five main gates. The whole network of fortifications was, however, in poor condition. To the north and the east, two narrow causeways built on dams extended across the lake through drawbridges, leading, respectively, to a Vauban-style citadel and the small suburb of San Giorgio.

The strategic role of Mantua is easy to understand, as it posed a constant threat to the lines of communication of any army conducting operations to the east and the north. In order either to link up with the French armies in Germany or bring war to the Austrian borders, Bonaparte had thus first to dispose of the fortress. On the other hand, Mantua was crucial to any Austrian attempt at retaking Lombardy. In 1796, moreover, the side holding Mantua enjoyed a remarkable political advantage. For those classes still supporting the ancien régime, the fall of the fortress to the French would mean the final victory of the Revolution in Italy. For France, the seizing of Mantua would signal the end of Austrian rule over northern Italy to the rest of Europe. The French blockade (and, for a limited period, the sieges) of Mantua took place from 3 June 1796 to the capitulation of the fortress on 2 February 1797, with a short interruption from 1 to 10 August, when Feldmarschall Dagobert Graf Würmser succeeded in temporarily relieving the city.

The sieges can be divided into four stages:

  1. 3 June-18 July 1796. After the conquest of Lombardy, on 30 May Bonaparte’s Armée d’Italie crossed the Mincio at Borghetto and repulsed Feldzeugmeister Johann Peter Freiherr von Beaulieu up to the Tyrol, thus severing any link between the Austrian field army and Mantua. By then, the fortress garrison under General Joseph Count Canto d’Yrles, had been brought up to 15,000 men (of whom 1,500 were unfit for service), with 315 pieces of artillery. Supplies for the troops and the 25,000 citizens were estimated to last three months. Bonaparte entrusted General Jean Sérurier’s division (9,000 men) with the investment of the fortress, which began on 3 June. For forty-five days the French, under the expert guide of General François de Chasseloup- Loubat, the Armée d’Italie’s engineer in chief, were busy completing the encirclement of the fortress and preparing earthworks for the siege artillery emplacements. Bonaparte also ordered the assembly of a boat flotilla to patrol the lake. During this period the Austrians attempted limited sorties and only occasional fighting broke out along the siege lines.
  2. 18 July-1 August. On 18 July the blockade became a bona fide siege, as heavy guns and mortars started striking the bastions and the city. During two weeks of bombardment more than 12,000 explosive projectiles (that is, excluding round shots) fell on Mantua.
  3. 1 August-15 September. Over the night of 31 July- 1 August, Würmser’s advance from the Tyrol forced Bonaparte hastily to lift the siege. The city was resupplied, and the garrison brought within the walls the siege equipment the French had left behind (179 guns and thousands of shot). After Würmser’s defeat at Castiglione on 5 August, however, the link between Mantua and the field army was once again severed. Now without siege artillery, French general Jean Joseph Sahuguet, who had temporarily replaced Sérurier in command, could only make dispositions for a blockade that prevented the Austrians from acquiring supplies from the surrounding area. By then, the garrison had risen to 16,500 (of which 12,200 were fit for service). In early September Würmser’s second offensive failed miserably. Defeated at Bassano and cut off from the rest of his army, the Austrian commander in chief nevertheless ably eluded the French pursuit and managed to reach Mantua with around 13,000 men. After two days of fighting before the city ramparts, at La Favorita and San Giorgio, on 15 September Würmser was forced to retire within the fortress.
  4. 15 September 1796-2 February 1797. With Würmser’s arrival, the garrison strength rose to almost 30,000 men. More troops, however, meant more mouths to feed. Shortages in supplies began to tell, and Würmser was obliged to organize foraging sorties. Against disease, however, there was nothing he could do, and in the following six weeks 4,000 men died in the hospitals. Aware that Mantua could not resist for much longer, Austrian officials in Vienna prepared a new campaign. Feldzeugmeister Joseph Alvinczy Freiherr von Berberek twice failed to relieve Mantua. In November his advance was checked at Arcola. On 14 January 1797, while Bonaparte crushed the main Austrian army at Rivoli, a secondary Austrian Korps under Generalmajor Giovanni, Marquis Provera (5,000 men) succeeded in breaking through the French line on the Adige and arrived before Mantua. Bonaparte, however, immediately rushed back from Rivoli, with General André Masséna’s and General Claude Victor’s divisions. On the sixteenth, Provera tried to make his way to the citadel and join Würmser. Attacked by superior forces at La Favorita, he was forced to surrender his entire command. Alvinczy’s second failure sealed the fate of Mantua, where starvation and disease continued to exact a high daily toll. On 2 February, Würmser accepted the French conditions to capitulate.

References and further reading Boycott-Brown, Martin. 2001. The Road to Rivoli: Napoleon’s First Campaign. London: Cassell. Cuccia, Phillip. 2001. “The Key to the Quadrilateral: An Analysis of the Sieges of Mantua During the Napoleonic Wars.” Ph. D. diss., Florida State University. Esposito, Vincent J., and John R. Elting. 1999. A Military History and Atlas of the Napoleonic Wars. London: Greenhill. Voykowitsch, Bernhard. 1998. Castiglione 1796: Napoleon Repulses Würmser’s First Attack. Maria Enzersdorf: Helmet.